This invention relates generally to a system and method for shifting a bicycle between gears, and in particular to a system and method for shifting a bicycle between gears using a handlebar-mounted shifter.
Early bicycles typically had a single gear which in combination with a bicycle chain and pedals translated circular motion of a bicycle rider's feet into rotation of a rear wheel. These single gear bicycles provided the rider of the bicycle with a method of transportation, but were not very efficient. Soon, bicycles with three, ten or twenty-one different speeds (e.g., different gears) were created which permitted the rider of the bicycle to select a particular speed and gear to use for a particular type of terrain. For example, a low gear may be used for climbing up a hill while a high gear may be used for riding down the other side of the hill. Typically, a seven gear cassette is rotatably mounted on the rear wheel of the bicycle and the chain of the bicycle was typically shifted between these gears by a rear derailleur mechanism. A front set of gears may also be provided. The rear derailleur is connected to a cable and a lever so that the rear derailleur mechanism translated movement of a rider's hand into shifting of the bicycle chain between gears.
Derailleur type shifting mechanisms for bicycles have typically been actuated by levers supported on some portion of the bicycle, such as the handlebars or the down tube of the bicycle. The levers require a rider to pull the lever back or push the lever forward in order to cause a gear shift of the bicycle. The levers also typically required the rider of the bicycle to remove his/her hands from the handlebar grips in order to actuate the shifter lever. The removal of the rider's hands from the handlebar may cause the rider to lose control of the bicycle. In addition, these levers may be difficult to actuate in muddy conditions. Thus, attempts were made to provide some system for permitting the rider of the bicycle to keep his/her hands on the handlebar of the bicycle while shifting the bicycle between gears.
This has led to the development of a system and method that permits the rider of a bicycle to actuate the shifting mechanism while keeping his/her hands on the handlebar is a grip shifter system and method in which a shift actuator is rotatably mounted on the handlebars so that a rider may shift the bicycle between gears without losing control of the bicycle. One conventional shift actuator is mounted on the handlebar of the bicycle outside of the brake actuator and nearest the end of the handlebar. The shifter may be actuated by rotating the grip. Due to the substantial width and diameter of this grip shift actuator, the pivot point for the brake lever is located some distance away from the rider's hand so that the angular rotation of the brake level is reduced. In addition, to rotate the shift actuator and to be able to actuate the brake lever attached to the brake actuator from one position, the brake lever has to extend a large distance over the shift actuator. The location of the brake lever and the large distance that it extended over the shift actuator make it more difficult for the rider of the bicycle to actuate the brakes of the bicycle because the brake lever had to be pulled a greater distance than typical brake systems. In addition, the position of the rider's hand to actuate the brake lever of the bicycle is not ergonomically correct.
This conventional handlebar-mounted shift actuator also has a metal spring inside the shift actuator which permits the rider of the bicycle to precisely shift between different gears, which is known as index shifting. The metal spring is mounted on an inner drum of the shift actuator. The conventional handlebar-mounted shift actuator also has a clamp, separate from the spring, which secured the actuator to the handlebar of the bicycle. The clamp and spring each had a predetermined thickness, and the thickness of the combination of the clamp and the spring increases the overall diameter of the shift actuator which increases the distance of the pivot point of the brake lever from the rider's hand which reduces the angular rotation of the brake lever during braking and made it difficult for a rider to actuate the brake lever of the bicycle. In addition, the increased diameter of the shift actuator makes it difficult for people with smaller hands to grip the brake lever.
Another conventional handlebar mounted shifter has a grip assembly on each of the handlebar attached to a shifter device. Each shifter device on each end of the handlebar has two levers attached to it which are mounted so that they are below the handlebar and may be actuated by the thumb of a rider. The shifter device has a ratchet within it and depressing the lever causes ratcheting of the ratchet which pulls the shifter cable and shifts the gears of the bicycle. Thus, when one lever is depressed, an upshift occurs while depressing the other level causes a downshift. Using the two shifter devices at each end of the handlebar, a rider may shift the front and rear derailleurs of the bicycle. These levers have a limited amount of surface area so that they may be difficult for a rider to depress the levers in wet or muddy conditions. The levers also permit the rider to apply only a limited amount of force to the levers to shift the gears of the bicycle which may pose a problem when the gears of the bicycle or the shifter cable are fouled with mud. There are also some shifters with regions which permit a rider to use his/her thumb to shift the bicycle, but these shifters do not position the rider's thumb in a good ergonomic position.
These conventional handlebar mounted shifters are not good ergonomic designs (i.e., the hand of the rider is not in a good ergonomic position) and do not fulfill the needs of a shifter mechanism that is often exposed to, for example, mud, which may make it more difficult to shift gears and thus increases the amount of torque that the rider must apply to shift the gears of the bicycle. Thus, due to the problems of these conventional handlebar mounted shifter systems, it is desirable to provide a handlebar-mounted shifting system which positions the rider's hands in an ergonomically correct position, does not make the actuation of the brake more difficult than a conventional braking system and permits a rider to apply more torque, as needed, to shift the gears of the bicycle in muddy conditions. In addition, it is desirable to provide a handlebar-mounted shifting mechanism which has a reduced overall thickness and diameter so that the brake lever does not have to extend a large distance over the shift actuator and the hands of the rider are in a more ergonomically correct position to actuate the brake. In addition, the reduced diameter shifter system has a pivot point of the brake lever which is closer to the rider's hand so that the angular rotation of the brake level is increased. It is also desirable to provide a single assembly with a clamp and a spring which reduces the overall diameter of the shifter mechanism. Thus, there is a need for a handlebar-mounted bicycle shifter system and method which avoid these and other problems of known systems and methods, and it is to this end that the present invention is directed.